A plurality of control devices for controlling or regulating the operational sequences in a motor vehicle are provided. These control devices, of which each controls or regulates a functional unit of the motor vehicle during operation, are connected to one another via a communications system.
In principle, the control devices can be subdivided into two categories. For one thing, there are the so-called individual control devices. These are control devices having an individual program and hardware, which are used, for example, for regulating the ABS system and the engine management system. For another thing, so-called control devices of similar construction are provided, such as control devices for regulating the elctromechanical brake (EMB). In the case of the EMB, four control units are providedxe2x80x94one per wheelxe2x80x94which are identically constructed and operated with the same software. The four control devices fulfill the same function, namely, adjusting the braking force according to a setpoint input.
When each individual wheel is regulated, the differences come about only from the specific positioning of the control unit. That is the case in a braking force distribution between front and rear axle, and in operating an ABS, ASR or ESP. In those cases, the control device has to know which wheel is to be regulated, since wheel-specific setpoint values are to be adjusted.
The control devices usually have a non-volatile program memory and a volatile memory. Programming is done once, and remains unchanged for the service life of the equipment. For a change in programming, the non-volatile memories of all the control devices have to be reprogrammed. Therefore, a later modification of the functional units of a motor vehicle prove to be extremely costly.
It is, therefore, an object of the present invention to provide a system for controlling or regulating the operational sequences of a motor vehicle, by which subsequent modifications are easily carried out. It is a further object to provide a method by which starting or initializing such a system can be carried out.
In the system of the present invention, the non-volatile memories in the control devices contain a loading routine. A main control device having a central memory, in which the programs of all the control devices for controlling/regulating are stored, is provided which makes possible indirect access to the control devices. The connecting elements make possible an identification of the respective control device.
Thus, the program for controlling the control devices are no longer in the non-volatile memories of each control unit, as it is known from the related art. Instead, they are stored in a central place in the central memory. This quite considerably simplifies subsequent modifications, e.g. with recall actions, since now the program changes have to be carried out at a central point, namely in the central memory. After start of the system, the control units first identify themselves with the aid of their connecting elements. Following that, by means of the loading programs in the non-volatile memories of the control units, the programs are loaded from the central memory into the non-volatile memories of the control units, via indirect memory access, and are subsequently processed.
Since the programs run in the volatile memory (the working memory (RAM)), a faster program run is achieved because of the shorter access times. It is also of advantage that only a relatively smaller non-volatile memory is still necessary. This saves costs.
Because of the indirect access method of the control units to the central memory, the internal data bus structure of the main control device can be chosen independently of the data bus structure of the control units.
For the central memory, the use of a mobile storage medium, such as a CD-ROM or a memory chip is preferred. Because of the independence of the data bus structures this is not a problem. Then, for subsequent modifications, only the mobile storage medium still has to be exchanged. If the driver takes the mobile storage medium with him when he leaves his motor vehicle, the vehicle is safe from theft. It is of advantage if the non-volatile memory is a BOOT-EPROM. These storage modules are available in various types.
As communications bus, a serial communication bus such as a CAN, a TTP/C or an RS 232 is preferably used.
In one advantageous embodiment of the present invention, the connecting elements for connecting the control devices to the communications bus are plug devices. These simplify the exchange of the control units. This exchangeability is made more advantageous if the plug connection devices have contact or terminal pins, whose coding makes possible the identification of the control units. Then, the position recognition and the function recognition of the control unit take place via the pin coding of the plug connection device.
The number of coded pins determines the number of possible combinations. Two bits are required for coding the four control units of the EMB, e.g. 00 for left front, 01 for right front, 10 for rear left and 11 for rear right.
However, for safety reasons the redundancy is raised, and coding is done using more than two bits.
The method according to the present invention for starting a system for control/regulation of the operational sequences in a motor vehicle, having a number of control units for controlling/regulating, which each have a volatile memory and a non-volatile memory, and having a main control device having a central memory, includes the following method steps:
After switching on the system, the identification of the individual control units takes place. Next, the loading programs in the non-volatile memories of the control units are started. The programs are loaded from the central memory into the volatile memories of the control units via an indirect memory access to the central memory. During the operation of the motor vehicle, these programs control the control units and, thereby, the operating of the motor vehicle.
Since there is no direct access of the control units to the program memory, quite different bus systems and memory configurations can be used in the control units, which are completely independent of the central memory.